What version are you running?
2.5.2
Describe the enhancement and the motivation for it.
We switched to hosting our git repositories with Atlassian Bitbucket Server (formerly Stash) and noticed that we no longer have a working RAW file URL mask.

Bitbucket Server, like its cloud counterpart, needs a commit id instead of a file object hash. I saw the base support for this is already there, so we'd just need to be able to define that somehow for a custom repository type, or have Bitbucket Server as a hosting vcs option available.
Please provide any additional information below.
I'd be more than happy to make a patch for this myself if I could get some pointers on what to modify. I already tried to adapt the get_file() and get_file_exists() method to also take a base_commit_id parameter and overwrite revision with it if present (just like in bitbucket.py), but it doesn't seem to be enough.